1. Field of the Invention
The present invention relates to a novel catalyst for oxidizing olefins into .alpha., .beta.-unsaturated aldehydes in the gaseous phase, to a process for preparing the novel catalyst, and to a process of preparing, .alpha., .beta.-unsaturated aldehydes in the presence of said catalyst. More particularly the invention relates to a novel catalyst comprising oxides of cobalt, molybdenum, bismuth, and iron.
2. Description of the Prior Art
The French Pat. No. 1,604,942 discloses a process for preparing acrolein by oxidizing propylene in the gaseous phase. According to this process a catalytic system is used which comprises a composition of oxides of molybdenum, bismuth, iron, and cobalt wherein the content of the various elements except oxygen is expressed as percentage by atoms as follows: molybdenum: 40-67.6%; bismuth: 1.9-21.7%, iron: 1.6-6.5% and cobalt: 21.0-48.1%. With these catalysts, the structure of which is completely ambiguous, only yields of 70% acrolein at the most can be achieved when 90% of the propylene are converted per single pass. According to the disclosure of the above patent the catalysts are prepared from salts of molybdenum, bismuth, iron and cobalt in the conventional manner by mixing amounts of the salts corresponding to the above cited atomic ratio, adding water or another solvent and heating the reaction mixture in order to cause the different components of the mixture to react with each other. This reaction mixture may then be fixed to a support or mixed with a diluent by milling. Subsequently, the material is calcined at a temperature of 450-550.degree. C. during 5 hours. The calcined material can be used directly or after compressing and milling it in order to increase its mechanical resistancy.